A variety of air filtration media constructions are currently available for use in filter elements designed to remove particulate contaminants from air streams. In particular, a wide range of media constructions have been developed for use in pleated filter elements. In addition to good particulate removal properties, suitable pleated filter media often has high strength, and preserves (or substantially preserves) the flat pleats of media during manufacture, storage and use.
In recent years, improved filter constructions have been created that utilize an alternative to pleated configurations. Specifically, these elements incorporate a series of fluted sheets of media through which air (or another gas) flows in a manner that the air flows from one flute to another as it passes from an upstream (“dirty”) side of the filter element to a downstream (“clean”) side of the filter element. This gas flow is often called “z-flow”, and sometimes referred to as a “z-flow element”. Example z-flow elements are disclosed in U.S. Pat. No. 8,241,383, assigned to Donaldson Company, Inc.
In some z-flow constructions, the flutes are characterized by unique shapes that contain features such sharp flute peaks and/or ridges formed in the fluted media between adjacent flute peaks. These z-flow constructions can reduce masking between fluted media and adjacent non-fluted media, which allows for more efficient use of media and increased media packing within specific element volumes. These constructions often also allow for media elements having different upstream and downstream volumes. These improved z-flow constructions with sharp flute peaks and ridges are examples of z-flow media with “structured flutes”. The structured flutes can provide improved performance relative to prior flutes that had a standard corrugated structure of undulating media lacking in sharp peaks and defined ridges.
Although z-flow media with structured flutes is desirable for many applications, much of the existing air filtration media can be difficult to form into structured flutes. Also, the media can become degraded (such as from tearing) during formation of the z-flow constructions, or the peaks and ridges (or other structures) in the flutes can fail to adequately retain their shape after forming and/or during use.
Therefore, a need exists for improved filter media which can be readily formed into structured flutes, which provides a desirable level of retention of flute shapes, and is otherwise suitable for use in media and media constructions having flutes with sharp peaks and ridges between peaks, as well as other formed structural elements.